rpc-coverage.sh: Make error messages explicit.
rpc-coverage.sh: Make error messages explicit.

Make failure explicit, with `set -e' script exits silently and we have
no way to know where it failed unless run by set -x.

Signed-off-by: Sachidananda Urs <sac@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 875 (Implement a new protocol to provide proper backward/forward compatibility)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=875

Kaushikbv/Gluster,Kaushikbv/Gluster,Kaushikbv/Gluster